Borax-sodium silicate stabilizers for peroxide bleaching



June 10, 1969- R. N. SUITER BORAXSODIUM SILICATE STABILIZE RS FOR PEROXIDE BLEACHING Filed June 14, 1966 BRIGHTNESS RESULTS OBTAINED WITH VARIOUS COMBINATIONS OF BORAX-SILICATE STABILIZER INCLUDING OPTiCAL DYE EFFECT zxculomc OPTICAL DYE EFFECT mmFmZOFUmJmum mMPZDI mU2 FUwJLuI m34m O PERCENT SILICATE IN STABlLIZER COMBINATION WITH BORAX INVENTOR ROGER N. SUITER A TORNEYV nited States 3,449,254 BORAX-SODIUM SILI'CATE STABILIZERS FOR PEROXIDE BLEACHING Roger N. Suiter, Camillus, N.Y., assignor to Allied Chemical Corporation, New York, N.Y., a corporation of New York Filed June 14, 1966, Ser. No. 557,461 Int. Cl. C11d 7/18, 7/14, 7/06 US. Cl. 252-99 6 Claims ABSTRACT OF THE DISCLOSURE Alkaline peroxide bleaching solutions must generally be stabilized to prevent excessive decomposition of the peroxide since such decomposition is wasteful, results in poor bleaching and may cause damage to the goods being bleached. Many variances dictate the selection of a particular stabilizer since it has a direct effect not only on the peroxide but on the properties of the bleached fabric product as well.

Bleaching of cotton cloth is not a matter of simply improving the whiteness of the cloth but also involves other properties which are equally as important as white-= ness. Cloth can be bleached to a high degree of whiteness by drastic treatment, but good quality cloth should have the following properties: (1) low fluidity, a measure of degradation of the cloth; (2) excellent absorbency, a physical property of the goods which relates to the ability to take up certain liquids into the fibers and which is important in determining the suitability of the fabric for particular uses, particularly when the fabric is to be dyed; and (3) freedom from motes which are seed fragments remaining in the cotton after ginning. The ultimate aim in the bleaching industry is obviously to prepare products which exhibit all of these desirable properties.

Sodium silicate, employed in peroxide bleaching compositions, while being the most effective in giving good overall properties, is frequently objectionable because it presents the serious problem of scaling of equipment which causes bruise marks or tearing of the fabric being bleached. Silicates are also deposited in the fabric which are difiicult to remove and subsequently give rise to dyeing difficulties. As a result of these difficulties, the indus try has turned to such stabilizers as borax as a substitute for or in combination with sodium silicate. However, bleaches stabilized with borax alone are less effective than sodium silicate-stabilized bleaches in that-they produce poorer brightness and slightly poorer mote removal. In the prior combinations wherein borax was substituted for only a small portion of sodium silicate, a large amount of sodium silicate was still present and failed to solve the problem of scaling and silicate deposition. There is therefore a continued need for eflicient stabilizers in peroxide bleaching.

It is, therefore, an object of this invention to provide bleaching solutions which will produce fabrics having high absorbencies and brightnesses, low fluidities and good mote removal while substantially reducing the scaling of equipment and deposition of silicates on the cloth.

It is a further object of the invention to provide an efiicient bleach composition for bleaching cotton knit goods which contains a reduced amount of sodium sili cate.

Other objects and advantages will be apparent as the invention is hereafter described in detail.

The above objects are realized by providing a bleaching composition comprising about 2.5 to 3.5 grams per liter of hydrogen peroxide, from about 1 to 6 grams, preferably 3 to 4 grams per liter of sodium hydroxide, 6 to 9 grams per liter of borax (Na B O -10H O) and sufficient sodium silicate to provide in the bleaching composition from about 0.75 to 1.60 grams per liter, preferably 0.80 to 1.1 grams per liter SiO and not more than an equal amount of Na O derived from said silicate solution. It has been found that the resulting peroxide bleach is not only superior to the corresponding bleach stabilized with borax alone, but additionally makes it possible to retain substantially the desirable properties received with sodium silicate while substantially reducing the scaling of equipment and deposition of silicates.

The above compositions are the result of the unexpected discovery that the brightness obtained when employing borax-sodium silicate mixtures is not a linear function of the amount of sodium silicate present in the solution. As illustrated in the drawing, wherein 42 B. sodium silicate is employed, the brightness obtained, excluding the optical dye effect, drops one unit as the 42 B. sodium silicate content is reduced from 100 to Then from 75% to 25% 42 B. sodium silicate there is a plateau in the curve. Below 25 42 B. sodium silicate the brightness falls off rapidly. The most desirable properties and minimum scaling and deposition result when proportions are employed corresponding to the plateau of the curve. While the reasons for the properties received when operating within this plateau are not known, the improved properties are not the result of the additive effect of the properties of the two stabilizers as will be shown below. The explanation appears to best lie in some coaction or cogcneric effect between borax and sodium silicate within the recited range which does not occur when employing larger amounts of sodium silicate.

For illustrative purposes, the bleaching solutions are employed in a process substantially as disclosed in US. Patent 3,142,531 issued July 28, 19-64 to S. M. Rogers. The cotton goods are immersed in a bath of an aqueous wetting-out solution containing an optical brightening agent and wetting agent and are then placed in a kier, Without rinsing, and bleached with the bleaching composition of this invention.

The brightness of the bleached cotton knit goods was determined using a Hunter D40 Reflectometer using the blue filter.

The capillary absorbency is determined by the following procedure: /2-in :h strips of conditioned cotton goods, cut in wale direction, are fastened without stretching between prongs projecting from the edge of two disks, spaced about 6 inches apart by means of a supporting rod passing through the center of each disk. The assembly is then placed in a vertical glass cylinder containing 1-1 /2 inches of distilled water. At the end of 5 minutes as determined by a stopwatch started simultaneously with placing the assembly in the cylinder, the height of the water absorption in the cotton strips is measured by means of a transparent scale attached to the outside of the cylinder by flexible bands. The zero point is adjusted to the water level and each 4 inch rise of water in the fabric is equivalent to 1 point of absorbency. The absorbency test is carried out at 73 F. and a relative humidity of 50%. A capillary absorbency of 25-30 is acceptable and absorbency above 30 is rated excellent.

A measurement of degradation or modification of the cotton fibers due to the chemicals used is very effectively silicate-stabilized bleach compositions while substantially eliminating the disadvantages normally encountered.

I claim:

1. A bleaching composition for cotton knit goods consisting essentially of from 25 to 3.5 grams per liter of 3. determined by determining the fluidity of the cotton cellulose dissolved in cuprammonium solution according to a standard procedure as specified in A.A.T.C.C. Test 82-1961. The fluidity values are measured in rhes, reciprocal poises, with values of about 6 being indicative of the degradation of cotton fibers and values below 4 hydrogen peroxide, 1 to 6 grams per liter sodium hydroxbeing indicative of superior strength of the fibers. ide, 6 to 9 grams per liter of borax and sufiicient sodium Mote removal is determined by a visual examination. silicate solution to provide in the bleaching composition The following comparative examples illustrate the infrom about 0.75 to 1.60 grams per liter SiO and not vention The procedure and compounds employed were more than an equal amount of Na O derived from said the same in each case with the variation of amounts as silicate solution. indicated. Seventy grams of greige jersey cotton knit 2. A composition according to claim 1 wherein said goods having a weight of 2.2 sq. yds./lb. were used. The bleaching solution consisting essentially of about 7.2 to goods were wet-out in a solution of 3.00 g.p.l. of an iso 8.1 grams per liter borax and sufficient sodium silicate octyl phenyl polyethoxy ethanol (Triton X-100) and solution to provide about 0.80 to 1.1 grams per liter of 0.696 g.p.l. of stilbene disulfonate optical brightener SiO and from 0.32 to about 0.65 gram per liter of Na O (Leucophor BS), for 3 minutes at 180 F. Without derived from said silicate solution. washing, the goods were squeezed to a 200% wet pick up 3. A composition according to claim 1 wherein said and piled in a glass kier. A bleach solution containing composition consisting essentially of about 6 grams per 10.00 g.p.l. of 35% hydrogen peroxide, 12.00 g.p.l. of a liter of borax and sufficient sodium silicate solution to stabilizer and 1.13 g.p.l. of sodium hydroxide was added, provide about 1.60 grams per liter of SiO and about 0.64 the liquor to cloth ratio in this addition being 12:1. The gram per liter of Na O derived from said silicate solution. knit goods were bleached for 5 hours at 180 F. Following 4. A bleaching composition for cotton knit goods bleaching, the kier was drained and the goods were given consisting essentially of about 3.5 grams per liter of 5-minute circulating rinses with separate portions of hot hydrogen peroxide, 1 gram per liter sodium hydroxide, 9 Water, cool water, 2.0 g.p.l. NaHSO and 0.7 g.p.l. grams per liter of borax and 3 grams per liter of sodium NaHSO after which the goods were removed from the silicate solution to provide about 0.80 gram per liter of kier and washed and dried on pin frames in a forced Si0 and about 0.32 gram per liter of Na O derived from circulation oven. said silicate solution.

TABLE* Example 1 2 3 4 5 e 7 s 9 10 G.p.l. 42 Be. sodium silicat solution providing 9 6 3 2. 4 1. 8 3 3 3 G.p.l. sodium silicat 3. 32 2. 22 1.11 88 .67 1.12 1.12 1.12 G.p.l. otNazO .94 .64 .32 .25 .19 .32 .32 .32 G.p.l. of Si0z 2. as 1. 58 .79 .63 .48 .80 .so .so G.p.l.Borax(Na2B4O1J0HzO) 12 3 e 9 9.6 10. 2 s. 1 7. 2 6 Percentage ratio of silicate solution to borax in stabi- V lizer mixture -1 100/0 0/100 75/25 50/50 25/75 20/8 15/85 27/73 294/706 33. 3/66.7 Brightness including opticaL. 90. 6 87.0 89.5 89. 5 89.5 88.1 87 89.3 88.1 88.8 Brightness excluding opticaL. 78. 4 75.1 77. 5 77. 4 77.3 76. 9 76.1 77. 3 77.2 77.2 .Absorbeney (Wale) a- 53 51 52 53 54 51 48 51 55 55 F1uidity(Rhes) 2.0 2.2 1.8 1.8 1.7 1.7 1. 7 1. 1. 5 1. 5 Mote removal rating G0od+ Good Good Good Good Good Good Falr Fair Fair Average results of three replicate trials.

Comparison of the results of Examples 1 to 7 shown in the preceding table and the drawing shows that while borax-stabilized bleach gives a brightness of about 3 units lower than the sodium silicate-stabilized bleach, the boraxsilicate mixture containing only 25% silicate which is equivalent to only 0.3 weight percent of the bleach solution gives a brightness only 1 unit lower than silicatestabilized bleach which corresponds to 1.20 weight per- 5. A method of bleaching cotton knit goods consisting essentially of subjecting said goods to the action of a bleaching composition as defined in claim 1.

6. A method of bleaching cotton knit goods comprising subjecting said goods to the action of a bleaching composition as defined in claim 4.

References Cited cent of the bleach solution. With less than 25% sodum UNITED STATES PATENTS silicate, the brightness values drop oil sharply to t ose obtained with borax alone. Examples 8 to 10 illustrate 2,397,193 3/1946 Miller 8111 2,858,183 10/1958 Potter 8111 that the borax content can be cut even lower in the 2,860,945 11/1958 Dustman 8111 XR combination with good brlghtness results although sacrificin somewhat the level of the mote removal 2,868,615 1/1959 Ben 8111 g 3,142,531 7/1964 Rogers 252 99 XR properties received. In all instances within the described range, the problems of scaling and of silicate deposit, were substantially eliminated.

It is readily apparent from the foregoing that this invention provides a useful, efficient and economical solu tion to the problem of retaining the advantages of sodium m MAYER WEINBLATT, Primary Examiner.

US. Cl. X.R. 

